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GENERAL46464
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Last modified
8/24/2016 8:20:17 PM
Creation date
11/23/2007 2:40:05 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
General Documents
Doc Date
9/25/1997
Doc Name
GEOTECHNICAL REPORT SYLVESTER GULCH SITE DEVEOLPMENT 9/16/97 - 9/21/97
From
MOUNTAIN COAL CO
To
MLR
Permit Index Doc Type
EXPLORATION
Media Type
D
Archive
No
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:/~ <br />Reporting Period September 16, 1997 -September 2l, 1997 Page 2 <br />Field Observations, Data Collection, and Ongoing Evaluations <br />A complete inspection was performed by MCC on September 20, 1997 to visually observe and evaluate the <br />stability of slopes within the project area. Data collection efforts and evaluation or revaluation of <br />specific areas of concern continues. Individual areas are discussed th detail in the following sections. <br />Supporting documentation is attached for your review. <br />Lower Sylvester Gulch Road: Excavation work continues in areas where water and slope stability <br />issues aze not of concern (between Stations 37 and 50). Drainage control measures are being installed <br />above or at the top of other cut slopes in advance of major excavation work. Excavation work for Wall <br />E base preparation (Station 51 to 54) began. Observation of the cleazed slopes showed no failures or <br />slumping on September 20, and no previously undiscovered springs were exposed. <br />The latest reading on inclinometer I-2 (September 19) shows no changes in magnitude or direction from <br />what was previously observed and reported. Inclinometer I-2 will be maintained and monitored during <br />construction and for the long term. Most of the survey prisms placed earlier this year are also <br />unaffected and will remain in place for long-term surface monitoring. A replacement location for <br />inclinometer I-4 has been determined, however, drill rig access to the location is impossible until tree <br />removal and some excavation work is complete. <br />Upper Sylvester Gulch Road: The new/residual failure at approximately Station 63+50 reported <br />last week did not reappear or show additional movement after the slope was regraded. As reported <br />previously, the failure mass was a distinct semi-circular wedge of soil approximately 8 feet high by 8 <br />feet thick by 60 feet long that split off the cut slope, and was probably caused by over steepened cuts. <br />Surface surveys continue to indicate no appreciable movement either above the cut slope or below the <br />fill area. Stability analyses and other evaluations of the failed fill area by Golder Associates and Barr <br />Engineering are due September 30. <br />Main Embankment (F-Wallsl: As reported previously, work on the F-Walls was halted on <br />September 12 due to small but increasing movements at depth observed in inclinometer 1-9 and I-10 on <br />either side of the embanlanent. Additional measurements taken on September 17 and September 19 <br />show a decreasing rate of movement, although incremental increases in cumulative movement did <br />continue. Foundation settlement has stopped, and pore pressures, as measured by the piezometers <br />installed under the embankment also stabilized or decreased slightly. th light of this information, MCC <br />re-evaluated the need for the as-designed full embankment height, and decided that the most prudent <br />course of action is to leave the embankment at its current height and increase the road grade from the <br />embankment to the ventilation facilities from 8% to approximately 9.3%. On September 18, the <br />embankment was completed to a final finished elevation of 6812 feet, or approximately 23 feet below <br />design, excluding base course. MCC will continue to monitor the inclinometers and piezometers. <br />Landing #2 Road: The light-use road to Landing #2 was inspected on September 20. Soil cut and <br />fill slopes appeared stable throughout the length of the road. Drainage ditches appear to be working <br />properly. <br />
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